The problem is probably coming from the fact that your operation inputs does not match your outputs. Send Email is waiting for a Document or a Document List. In your operations, your Zip gives you a blob (a file), that is kept by set context variable. So you need a way to give a Document to Send Email.

The solution is to use :

Push & Pop > Push Document

(or Push Document list) before the Get File Operation. It will push the document in a pile in the context. And then, just before the Send Email, use :

Push & Pop > Pop Document

Push and Pop Operations are operations that enables you to creates piles to temporary save document into the context.

However, I'm surprised that Studio does not tell you about this input/output problem…